The present invention relates to a differential limiting (or slip limiting) system capable of actively controlling a differential limiting action to a rotational speed difference between left and right drive wheels in accordance with a control signal.
One conventional example is shown in Japanse patent provisional publication No. 61-67629. This conventional control system includes a vehicle speed sensing means, and a controlling means for controlling a fluid pressure in accordance with the vehicle speed, and is arranged to control an engagement force (that is, a differential limiting force) of a friction clutch disposed between a differential case of a side gear by controlling the fluid pressure supplied to the friction clutch.
However, this conventional control system is arranged to increase the engagement force of the friction clutch when the vehicle speed becomes higher, and to decrease the clutch engagement force when the vehicle speed becomes lower. Therefore, when the driver changes the course of the vehicle from one lane to another at high vehicle speeds, an undermoment due to the differential limiting action is produced at the start of the turning operation of the steering wheel, so that the vehicle response is degraded. As shown in FIG. 14, the undermoment is produced when the direction M' of a moment due to the differential limiting action is opposite to a turning direction M of the vehicle. As shown in FIG. 15, an overmoment is produced when both directions M and M' are the same.